1. Field of the Invention
The invention relates to a transflective liquid crystal display and more particularly to the structuring of a reflective layer in the transflective LCD device to adjust chromatic properties between a reflective region and a transmissive region.
2. Description of the Related Art
Liquid crystal display (LCD) devices are typically classified as transmissive and reflective types according to the light source. The transmissive type LCD device uses a backlight module, in which incident light is absorbed, or passes through the LC layer, resulting in the disadvantages of faded color and reduced contrast ratio under a natural light source or an artificial exterior light source. Conversely, the reflective type LCD device uses ambient incident light from an exterior light source, resulting in superior performance and high contrast ratio under outdoor sunlight. Additionally, because of its low power consumption, the reflective type LCD device is found primarily in portable display products. The reflective type LCD device is however useless when the exterior light source is dark or blocked, and it is comparatively difficult to achieve high resolution for a full color display. Accordingly, transflective LCD devices have been developed to combine the advantages of the reflective type LCD device and the advantages found in transmissive type LCD devices. The transflective LCD device can employ well-known active driving processes, such as amorphous silicon thin film transistors (a-Si TFT) or low temperature polysilicon (LTPS) TFTs, which are applied to information products with low power consumption.
FIG. 1 is an exploded diagram of a conventional transflective LCD device. The transflective LCD device 10 comprises an upper substrate 12, a lower substrate 14, and a liquid crystal (LC) layer 16 interposed therebetween. On the inner surface of the lower substrate 14, a plurality of gate lines 18 and a plurality of data lines 20 intersect to define an array of pixel areas 22. Each of the pixel areas 22 comprises a pixel electrode layer 24 and a thin film transistor (TFT) device 26. The pixel electrode layer 24 has a transmissive region T and a reflective region R. The TFT device 26 is fabricated near the intersection of the gate line 18 and the data line 20, and is electrically connected to the corresponding pixel electrode layer 24.
On the inner surface of the upper substrate 12, a black matrix layer 28 is provided and has a plurality of openings corresponding to the pixel electrode layers 24, and a color filter layer 30 is formed in the openings of the black matrix layer 28. The color filter layer 30 is composed of a plurality of color element groups arranged in a designated form, and each color element group consists of a red element R, a green element G and a blue element B. In addition, a common electrode layer 32 is formed on the color filter layer 30.
Operation of the transflective LCD device 10 is described in the following. First, in reflective mode, external incident light is reflected from the reflective region R, and is directed toward the upper substrate 12. At this point, when electrical signals are applied to the reflective region R by the TFT device 26, the arrangement of LC molecules varies and thus the reflected light is colored by the color filter layer 30, thereby displaying a color image. Second, in transmissive mode, the light emitted from a backlight device passes through the transmissive region T. At this point, when the electrical signals are applied to the transmissive region T by the TFT device 26, the arrangement of LC molecules varies and thus the light passing through the transflective LCD device 10 is colored by the color filter layer 30, thereby forming a color image.
Since each pixel area 22 has a reflective region R and a transmissive region T, light passes through the color filter layer 30 twice in reflective mode, and only once in transmissive mode, resulting in color shift therebetween. In conventional designs for the pixel areas 22, the pixel measurements corresponding to the red element R, green element G and the blue element B are identical, thus limiting adjustment margin for improving chromatic properties of the reflective region R. In this case, the color image displayed is yellowish due to a yellowish white point problem in the reflective region R.